Electrodeposition of alloys of molybdenum with cobalt, nickel, and iron



Patented June 3, 1952 ELEo'raon rosITloN F ALLOYS MOLYBDENUM WITHCOBALT, NICKEL,

AND IRON Matthew L. Holt, Madison, Wis., andHenry J. assignors toWisconsin Alumni Research Foundation, Madison, Wis., a corporation ofWisconsin No Drawing. Application March 10, 1950, Serial No. 149,022

Seim, Reno, N ev.,

This invention relates, generally, to the electrodeposition ofmolybdenum alloys and it has particular relation to theelectrodeposition of alloys of molybdenum with cobalt, nickel or iron.

Among the objects of this invention are: To provide for theelectrodeposition of alloys of molybdenum with cobalt, nickel and iron;to improve the current efficiency in the electrodeposition process; toincrease the molybdenum content of the alloy deposited on the cathode;and to provide a new bath for use in accomplishing these iron), such asthe sulfate, ammonium hydroxide and Water. Electrolysis of this platingbath using soluble anodes, such as cobalt, nickel, iron, or molybdenumanodes, or an insoluble anode, such as platinum, effects the depositionof an .alloy 14 Claims. (01. 2o4 43) of molybdenum with the alloyingmetal (cobalt;

nickel or iron) on the cathode. The cathode may be formed of anysuitable material such as 'plati-' num, gold, copper, iron, nickel,cobalt, brass, or other metals or alloys. While the temperature of theplating bath may vary from room tempera-j ture to the boiling point ofthe solution, best re suits are obtained when it is kept at atemperatureof from 20 to 30 C. There appears to be no critical cathodecurrent density for the plating bath. The optimum current density isdependent on other electrolysis conditions and the composition of thebath. Cathode current densities that have been found to be satisfactoryvary from about 1 ampere per square decimeter to 22.2 amperes per squaredecimeter. Experimental work in connection with this invention showsthat the concentration of the alloying metal compound in the platingbath is not critical. However, it was found that the amount ofcomplexing agent, citric acid in accordance with this invention, whichis required depends upon the amount of alloying metal compound which ispresent. While the amount of the complexing agent is not critical, itappears that, when citric acid is employed, arslight excess of it overthe amount of alloying metal compound is required. Preferably a ratio ofabout 1.5 moles of citric acid to one mole of the alloying metal isemployed.

The amount of the soluble molybdate compound which is used to provide agood alloy deposit on the cathode varies according to the electrolysisconditions. In accordance with this invention sodium molybdate isemployed. Satis factory alloy deposits have been obtained from baths ofthe present invention containing less than two grams per liter and asmuch as forty grams per liter of sodium molybdate. The use of four gramsof sodium molybdate per liter gives excellent results.

In order to obtain satisfactory alloy deposits on the cathode it isnecessary to control the pH of the plating bath. While alloy deposits ofmolybdenum can be obtained from plating baths of the present inventionwith a range of pH from three to nine, it appears, in general, when thebath is neutral or basic (pH '7 to 9), higher cathode current densitiesare required. For the cobalt-molybdenum bath, a pH of 4 appears to bemost satisfactory. For the nickel-molybdenum bath, a pH of either fouror eight is satisfactory. For the iron-molybdenum bath, a pH of six wasfound to give optimum results. In accordance 1 with this inventionammonium hydroxide is employed foradjusting the pH of the bath.

. Cobalt-molybdenum plating bath.

Cobalt sulfate heptahydrate I -grams- 60 Citric acid do 66 Sodiummolybdate do 4 Ammonium hydroxide sufiicient to provide a pH of 4 Waterto give a total volume of 1 liter Temperature of 25 C.

With the cobalt-molybdenum bath adjusted to a pH of 4, electrolysis atten amperes per square decimeter deposited a cobalt-molybdenum alloy onthe cathode containing 6.9 per cent molybdenum with a cathode currentefilciency of 36 per cent. When the pH of the bath was increased to six,electrolysis at the same current density deposited an alloy on thecathode containing 27.2

per cent molybdenum at a cathode current efficiency of 4.0;per :cent.

Nickel-molybdenum plating bath Nickel sulfate hexahydrate grams 6.0Citric acid ...do 66 Sodium molybdate. ;do .4

Ammonium hydroxide sufflcient'to provide the required pH- Water to givea total volumeiof l' liter Temperature of 25 C.

With a bath pH of 4 and a current densityci ten amperes per squaredecimeter, the nickel molybdenum alloy deposit on the cathode-contained13 per cent molybdenum and the cathode current efficiency was 24 percent. when thegpH of the bath was increased to 8, electrolysis at thissame current density deposited an alloy .onthe cathode containing I518,per cent molybdenum with a cathode current eficiency of 62 per cent.

I ron-molyb'denum platinghain Ferrous suliatemeptahydrate grams -60Citric acid ..'.do 166 Sodium 'inolybdate do ,4

I Ammonium hydroxide sufficient to provide .the

required pH Waterto give atetal volume of 1 liter. Temperature of 25 C.

When the pH ofthe bath was" adjusted tofi, electrolysis at 10 amperesper-sq-uare decimeter deposited an alloy'on' the cathode containing'48.6per .cent molybdenum"-at a cathode current erficiency of 17 per cent. Onincreasing the pH of thebath to '7,'electrolysis' at the same currentdensity deposited an alloy'containing 62'per cent molybdenum with acurrenvefficiency or 13 .per

cent.

'Whatis claimed-asnew is:

1. Method of 'ele'ctrodepositing "an alloy :of

molybdenum and a metal of the 'classconsijsting of" cob alt, nickel andiron which comprises "passing current between an-anode and *a cathode onwhich the alloy is to-bedeposited in-an' aqueous electrolyte consistingessentially of "60 grams per liter ofa sulfate selecte'cl'irom the'classcons-isting ofcobalt, nickel and iron,-citrie acid in an ing currentbetween an anodeand alcalthodeon which the alloy is to be depositedjinanaqueous electrolyte consistingressentiallylOFSDgramsper liter of asulfate selectedfrom the class .cons'isting of cobalt, nickelandliron,.66 grams per'liter of citric acid, 4 grams per liter.oflsodiummoldybe 4date, and suflicient ammonium hydroxide to provide a pH ranging from 4to 8.

5. The invention, as set forth in claim 4, wherein the cathode currentdensity ranges from 1 to 22.2 amperes per square decimeter.

6. A bath for electrodepositing an alloy of molybdenum and a metal ofthe class consistin of cobalt, nickel and iron consisting essentially ofan aqueous electrolyte containing grams per 'liter "of *azisulfateselectedifrom theiclass consist- *ing"of'cobalt, nickel and iron, citric'acid in an amount in excess of the sulfate, 2 to40 grams per "liter ofsodium molybdate, and sumcient amwmoniumhydroxide to provide a pH offrom 4 to 8.

':'7. .Theinvention, as set forth in claim 6, wherein 1.5 molesmf citricacid are used to one mole of sulfate.

"8, A bath for ;electrodepositing an alloy of fmolybdenumand a metal ofthe class consistin ..,ofco.ba1t,...mcke1 and iron consistingessentially of an aqueous electrolyte containing 60 grams per "liter ofrasuliateselected from the class consisting of cobalt, nickel and iron,66 grams per liter oicitrio-acid, 4 grams per liter of sodium molybdate,and sufiicient ammonium hydroxide to pro vide apHof from 4 to 8. 1

"9. A .hath for electrodepositing an alloy .of molybdenum anda metal of.the class consisting of cobalt, nickel and iron consistingessentiallyor:

"Sulfate selectedfrom theclass consisting- 01' cobalt, nickel and' irongrams -60 'Citric acid ;do '66 Sodium molybdate do 4 Ammonium hydroxidesuflicient to 'pr'ovide a pHrangin'g from 4 to 8. "Waterto'give avolumeof Iliter.

.10. A bath for :electrodepositing :ran szalloy of molybdenum andcobalt' consisting :essentially of Water :togivea volume of 1. liter.

11. A bath :for electro'depositing an ;,alloy "of molybdenum and cobaltconsisting essentially of Cobalt V sulfate heptahydrate .grams- 6OCitric racid do 66 "Sodiummolybdate' do 4 -Ammonium""hydroxidesufiic'ient to provide s.

pI-I of G. I Water'togivea volume of 1 liter.

12. A bath for electrodepositing arr-"alloy 10f molybdenum and nickelconsisting essentially ;of

Nickel sulfate hexahydrate. "grams" '6 Citric. acid do.. 66Sodium-,mo1ybdate. do 1-4 Ammonium. hydroxide sufiicientto providea pHof 4. Water to ggive a volume of 'lyliter.

13. A bath for .electrodepositing ,an alloy ..of molybdenum. and nickelconsistingressentiallyrof2 l lick'el sulfate hexahydrate "grams" 60"Citric --acid -do 66 *Sodiumrmol'ybdate do '4 Ammonium hydroxidesufficient to providea pH1of8. "Water. to give a volume .of I. 1' liter.

14. A bath for electrodepositing an alloy of molybdenum and ironconsisting essentially of:

Ferrous sulfate heptahydrate "grams" 60 Citric acid do 66 r Sodiummolybdate do 4 Ammonium hydroxide sufficient to. provide a,

pH of '6. Water to give a volume of 1 liter.

MATTHEW L. HOLT. HENRY J. SEIM.

6 REFERENCES CITED 7 The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 2,160,322 Armstrong et a1. May30, 1939 2,428,404 Yntema, Oct. 7, 1947 OTHER REFERENCES Metal Industry,Nov. 22, 1946, pp. 434, 435, 436 (an article by L. E. Valler and M. L.Holt).

1. METHOD OF ELECTRODEPOSITING AN ALLOY OF MOLYBDENUM AND A METAL OF THECLASS CONSISTING OF COBALT, NICKEL AND IRON WHICH COMPRISES: PASSINGCURRENT BETWEEN AN ANODE AND A CATHODE ON WHICH THE ALLOY IS TO BEDEPOSITED IN AN AQUEOUS ELECTROLYTE CONSISTING ESSENTIALLY OF 60 GRAMSPERLITER OF A SULFATE SELECTED FROM THE CLASS CONSISTING OF COBALT,NICKEL AND IRON, CITRIC ACID IN AN AMOUNT IN EXCESS OF THE SULFATE, 2 TO40 GRAMS PER LITER OF SODIUM MOLYBDATE, AND SUFFICIENT AMMONIUMHYDROXIDE TO PROVIDE A PH OF FROM 4 TO 8.